Modelling of rheological and ageing properties of bitumen based on its chemical structure

The aim of this research was the construction of a model to describe the rheological and the ageing behaviour of bitumen by its chemical properties. Therefore, linear combinations were determined considering the contents and the average molecular weights Mn of the four substantial fractions of bitumen. These substantial fractions are the SARA fractions consisting of the saturates, aromatics, resins and asphaltenes. The determined linear combinations allow the description and prediction of different conventional and rheological parameters like the softening point TR&B and the needle penetration PEN as well as the complex shear modulus |G*| and the phase angle δ at different temperatures. Furthermore, the ageing behaviour was captured by ageing indices calculated by the ratio between the mentioned parameters in the long term aged state and the unaged state of the binder. These ageing indices can also be estimated by the SARA fractions, namely the SARA fractions of the unaged state of the bitumen. Due to these results the contents and molecular weights of the SARA fractions permit a description and prediction of the physical, rheological and ageing related properties of the bitumen. Thereby, the results of this research indicate that the influence of the SARA fractions on the behaviour of bitumen decreases with decreasing temperature.